Elastic substantialy linear olefin polymers

ABSTRACT

Elastic substantially linear olefin polymers are disclosed which have very good processability, including processing indices (PI&#39;s) less than or equal to 70 percent of those of a comparative linear olefin polymer and a critical shear rate at onset of surface melt fracture of at least 50 percent greater than the critical shear rate at the onset of surface melt fracture of a traditional linear olefin polymer at about the same I 2  and M w  /M n . The novel polymers have higher low/zero shear viscosity and lower high shear viscosity than comparative linear olefin polymers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part of pending application Ser.No. 07/776,130, filed Oct. 15, 1991, pending the disclosure of which isincorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to elastic substantially linear olefin polymershaving improved processability, e.g., low susceptibilty to meltfracture, even under high shear stress conditions. Such substantiallylinear ethylene polymers have a critical shear rate at the onset ofsurface melt fracture substantially higher than, and a processing indexsubstantially less than, that of a linear polyethylene at the samemolecular weight distribution and melt index.

BACKGROUND OF THE INVENTION

Molecular weight distribution (MWD), or polydispersity, is a well knownvariable in polymers. The molecular weight distribution, sometimesdescribed as the ratio of weight average molecular weight (M_(w)) tonumber average molecular weight (M_(n)) (i.e., M_(w) /M_(n)) can bemeasured directly, e.g., by gel permeation chromatography techniques, ormore routinely, by measuring I₁₀ /I₂ ratio, as described in ASTM D-1238.For linear polyolefins. especially linear polyethylene, it is well knownthat as M_(w) /M_(n) increases, I₁₀ /I₂ also increases.

John Dealy in "Melt Rheology and Its Role in Plastics Processing" (VanNostrand Reinhold, 1990) page 597 discloses that ASTM D-1238 is employedwith different loads in order to obtain an estimate of the shear ratedependence of melt viscosity, which is sensitive to weight averagemolecular weight (M_(w)) and number average molecular weight (M_(n)).

Bersted in Journal of Applied Polymer Science Vol. 19, page 2167-2177(1975) theorized the relationship between molecular weight distributionand steady shear melt viscosity for linear polymer systems. He alsoshowed that the broader MWD material exhibits a higher shear rate orshear stress dependency.

Ramamurthy in Journal of Rheology, 30(2), 337-357 (1986), and Moynihan,Baird and Ramanathan in Journal of Non-Newtonian Fluid Mechanics, 36,255-263 (1990), both disclose that the onset of sharkskin (i.e., meltfracture) for linear low density polyethylene (LLDPE) occurs at anapparent shear stress of 1-1.4×106 dyne/cm², which was observed to becoincident with the change in slope of the flow curve. Ramamurthy alsodiscloses that the onset of surface melt fracture or of gross meltfracture for high pressure low density polyethylene (HP-LDPE) occurs atan apparent shear stress of about 0.13 MPa (1.3×10⁶ dynes/cm²).

Kalika and Denn in Journal of Rheology, 31, 815-834 (1987) confirmed thesurface defects or sharkskin phenomena for LLDPE, but the results oftheir work determined a critical shear stress of 2.3×10⁶ dyne/cm²,significantly higher than that found by Ramamurthy and Moynihan et al.International Patent Application (Publication No. WO 90/03414) publishedApr. 5, 1990, discloses linear ethylene interpolymer blends with narrowmolecular weight distribution and narrow short chain branchingdistributions (SCBDs). The melt processibility of the interpolymerblends is controlled by blending different molecular weightinterpolymers having different narrow molecular weight distributions anddifferent SCBDs.

Exxon Chemical Company, in the Preprints of Polyolefins VIIInternational Conference, page 45-66, Feb. 24-27 1991, disclose that thenarrow molecular weight distribution (NMWD) resins produced by theirEXXPOL™ technology have higher melt viscosity and lower melt strengththan conventional Ziegler resins at the same melt index. In a recentpublication, Exxon Chemical Company has also taught that NMWD polymersmade using a single site catalyst create the potential for melt fracture("New Specialty Linear Polymers (SLP) For Power Cables," by MonicaHendewerk and Lawrence Spenadel, presented at IEEE meeting in Dallas,Tex., September, 1991).

Previously known narrow molecular weight distribution linear polymersdisadvantageously possessed low shear sensitivity or low I₁₀ /I₂ value,which limits the extrudability of such polymers. Additionally, suchpolymers possessed low melt elasticity, causing problems in meltfabrication such as film forming processes or blow molding processes(e.g., sustaining a bubble in the blown film process, or sag in the blowmolding process etc.). Finally, such resins also experienced meltfracture surface properties at relatively low extrusion rates therebyprocessing unacceptably.

SUMMARY OF THE INVENTION

Elastic substantially linear olefin polymers have now been discoveredwhich have unusual properties, including an unusual combination ofproperties, which leads to enhanced processability of the novelpolymers. The substantially linear olefin polymers have the processability similar to highly branched low density polyethylene, but thestrength in toughness of linear low density polyethylene. Thesubstantially linear olefin polymer are characterized as having acritical shear rate at onset of surface melt fracture of at least 50percent greater than the critical shear rate at the onset of surfacemelt fracture of a linear olefin polymer having about the same I₂ andM_(w) /M_(n).

The elastic substantially linear olefin polymers also have a processingindex (PI) less than or equal to about 70% of the PI of a comparativelinear olefin polymer at about the same I₂ and M_(w) /M_(n).

The elastic substantially linear olefin polymers also have a melt flowratio, I₁₀ /I₂,≧5.63, and a molecular weight distribution, M_(w) /M_(n),defined by the equation:

    M.sub.w /M.sub.n ≦(I.sub.10 /I.sub.2)-4.63.

Compositions comprising the substantially linear olefin polymer and atleast one other natural or synthetic polymer are also within the scopeof the invention.

Elastic substantially linear olefin polymers comprising ethylenehomopolymers or an interpolymer of ethylene with at least one C₃ -C₂₀α-olefin copolymers are especially preferred.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 graphically displays dynamic shear viscosity data for an elasticsubstantially linear olefin polymer of the present invention and for acomparative linear polymer made using single site catalyst technology.

DETAILED DESCRIPTION OF THE INVENTION

Other properties of the substantially linear polymers include:

a) a density from about 0.85 grams/cubic centimeter (g/cm³) to about0.97 g/cm³, and

b) a melt index, I₂, from about 0.01 grams/10 minutes to about 1000gram/10 minutes.

Preferably the melt flow ratio, I₁₀ /I₂, is from about 7 to about 20.

The molecular weight distribution (M_(w) /M_(n)) is preferably less thanabout 5, especially from about 1.5 to about 2.5, and most preferablyfrom about 1.7 to about 2.3.

Throughout this disclosure, "melt index" or "I₂ " is measured inaccordance with ASTM D-1238 (190° C./2.16 kg); "I₁₀ " is measured inaccordance with ASTM D-1238 (190° C./10 kg).

The melt tension of these new polymers is also surprisingly good, e.g.,as high as about 2 grams or more, especially for polymers which have avery narrow molecular weight distribution (i.e., M₂ /M_(n) from about1.5 to about 2.5).

The substantially linear polymers of the present invention can behomopolymers of C₂ -C₂₀ α-olefins, such as ethylene, propylene,4-methyl-1-pentene, etc., or they can be interpolymers of ethylene withat least one C₃ -C₂ α-olefin and/or C₂ -C₂₀ acetylenically unsaturatedmonomer and/or C₄ -C₁₈ diolefins. The substantially linear polymers ofthe present invention can also be interpolymers of ethylene with atleast one of the above C₃ -C₂₀ α-olefins, diolefins and/oracetylenically unsaturated monomers in combination with otherunsaturated monomers.

Monomers usefully polymerized according to the present inventioninclude, for example, ethylenically unsaturated monomers, acetyleniccompounds, conjugated or nonconjugated dienes, polyenes, carbonmonoxide, etc. Preferred monomers include the C₂ -C₁₀ α-olefinsespecially ethylene, 1-propene, isobutylene, 1-butene, 1 hexene,4-methyl-1-pentene, and 1-octene. Other preferred monomers includestyrene, halo- or alkyl substituted styrenes, tetrafluoroethylene,vinylbenzocyclobutane, 1,4-hexadiene, and naphthenics (e.g., cyclopentene, cyclo-hexene and cyclo-octene).

Other unsaturated monomers usefully polymerized according to the presentinvention include, for example, ethylenically unsaturated monomers,conjugated or nonconjugated dienes, polyenes, etc. Preferred monomersinclude the C₂ -C₁₀ α-olefins especially ethylene, 1-propene,isobutylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Otherpreferred monomers include styrene, halo- or alkyl substituted styrenes,tetrafluoroethylene, vinylbenzocyclobutane, 1,4-hexadiene, andnaphthenics (e.g., cyclopentene, cyclohexene and cyclooctene).

The term "substantially linear" polymers means that the polymer backboneis substituted with about 0.01 long chain branches/1000 carbons to about3 long chain branches/1000 carbons, more preferably from about 0.01 longchain branches/1000 carbons to about 1 long chain branches/1000 carbons,and especially from about 0.05 long chain branches/1000 carbons to about1 long chain branches/1000 carbons.

The term "linear olefin polymers" means that the olefin polymer does nothave long chain branching. That is, the linear olefin polymer has anabsence of long chain branching, as for example the traditional linearlow density polyethylene polymers or linear high density polyethylenepolymers made using Ziegler polymerization processes (e.g., U.S. Pat.No. 4,076,698 or U.S. Pat. No. 3,645,992, the disclosures of which areincorporated herein by reference). The term "linear olefin polymers"does not refer to high pressure branched polyethylene, ethylene/vinylacetate copolymers, or ethylene/vinyl alcohol copolymers which are knownto those skilled in the art to have numerous long chain branches.

Long chain branching is defined herein as a chain length of at leastabout 6 carbons, above which the length cannot be distinguished using ¹³C nuclear magnetic resonance spectroscopy. The long chain branch can beas long as about the same length as the length of the polymer back-bone.

Long chain branching is determined by using ¹³ C nuclear magneticresonance (NMR) spectroscopy and is quantified using the method ofRandall (Rev. Macromol. Chem. Phys., C₂₉ (2&3), p. 285-297), thedisclosure of which is incorporated herein by reference.

"Melt tension" is measured by a specially designed pulley transducer inconjunction with the melt indexer. Melt tension is the load that theextrudate or filament exerts while passing over the pulley at thestandard speed of 30 rpm. The melt tension measurement is similar to the"Melt Tension Tester" made by Toyoseiki and is described by John Dealyin "Rheometers for Molten Plastics", published by Van Nostrand ReinholdCo. (1982) on page 250-251.

The SCBDI (Short Chain Branch Distribution Index) or CDBI (CompositionDistribution Branch Index) is defined as the weight percent of thepolymer molecules having a comonomer content within 50 percent of themedian total molar comonomer content. The CDBI of a polymer is readilycalculated from data obtained from techniques known in the art, such as,for example, temperature rising elution fractionation (abbreviatedherein as "TREF") as described, for example, in Wild et al, Journal ofPolymer Science. Poly. Phys. Ed., Vol. 20, p. 441 (1982), or in U.S.Pat. No. 4,798,081, both disclosures of which are incorporated herein byreference. The SCBDI or CDBI for the new polymers of the presentinvention is preferably greater than about 30 percent, especiallygreater than about 50 percent.

A unique characteristic of the presently claimed polymers is a highlyunexpected flow property where the I₁₀ /I₂ value is essentiallyindependent of polydispersity index (i.e. M_(w) /M_(n)). This iscontrasted with conventional polyethylene resins having rheologicalproperties such that as the polydispersity index increases, the I₁₀ /I₂value also increases.

The density of the ethylene or ethylene/α-olefin substantially linearolefin polymers in the present invention is measured in accordance withASTM D-792 and is generally from about 0.85 g/cm³ to about 0.97 g/cm³,preferably from about 0.85 g/cm³ to about 0.9 g/cm³, and especially fromabout 0.85 g/cm³ to about 0.88 g/cm³.

The molecular weight of the ethylene or ethylene/α-olefin substantiallylinear olefin polymers in the present invention is convenientlyindicated using a melt index measurement according to ASTM D-1238,Condition 190° C./2.16 kg (formally known as "Condition (E)" and alsoknown as I₂). Melt index is inversely proportional to the molecularweight of the polymer. Thus, the higher the molecular weight, the lowerthe melt index, although the relationship is not linear. The melt indexfor the ethylene or ethylene/α-olefin substantially linear olefinpolymers used herein is generally from about 0.01 grams/10 minutes (g/10min) to about 1000 g/10 min, preferably from about 0.01 g/10 min toabout 100 g/10 min, and especially from about 0.01 g/10 min to about 10g/10 min.

Additives such as antioxidants (e.g., hindered phenolics (e.g., Irganox®1010), phosphites (e.g., Irgafos® 168)), cling additives (e.g., PIB),antiblock additives, pigments, and the like can also be included in thepolyethylene compositions, to the extent that they do not interfere withthe enhanced properties discovered by Applicants.

The compositions comprising the substantially linear olefin polymers areformed by any convenient method, including dry blending the individualcomponents and subsequently melt mixing, either directly in the extruderused to make the finished article (e.g., film), or by premelt mixing ina separate extruder. The polyethylene compositions may also be preparedby multiple reactor polymerization techniques. For example, one reactormay polymerize the constrained geometry catalyzed polyethylene andanother reactor polymerize the heterogeneous catalyzed polyethylene,either in series or in parallel operation.

The improved melt elasticity and processibility of the substantiallylinear polymers according to the present invention result, it isbelieved, from their method of production. The polymers may be producedvia a continuous (as opposed to a batch) controlled polymerizationprocess using at least one reactor, but can also be produced usingmultiple reactors (e.g., using a multiple reactor configuration asdescribed in U.S. Pat. No. 3,914,342) at a polymerization temperatureand pressure sufficient to produce the interpolymers having the desiredproperties. According to one embodiment of the present process, thepolymers are produced in a continuous process, as opposed to a batchprocess. Preferably, the polymerization temperature is from about 20° C.to about 250° C., using constrained geometry catalyst technology. If anarrow molecular weight distribution polymer (M_(w) /M_(n) of from about1.5 to about 2.5) having a higher I₁₀ /I₂ ratio (e.g. I₁₀ /I₂ of about 7or more, preferably at least about 8, especially at least about 9) isdesired, the ethylene concentration in the reactor is preferably notmore than about 8 percent by weight of the reactor contents, especiallynot more than about 4 percent by weight of the reactor contents.Preferably, the polymerization is performed in a solution polymerizationprocess. Generally, manipulation of I₁₀ /I₂ while holding M_(w) /M_(n)relatively low for producing the novel polymers described herein is afunction of reactor temperature and/or ethylene concentration. Reducedethylene concentration and higher temperature generally produces higherI10/I₂.

Molecular Weight Distribution Determination

The whole interpolymer product samples and the individual interpolymersamples are analyzed by gel permeation chromatography (GPC) on a Waters150° C. high temperature chromatographic unit equipped with three mixedporosity columns (Polymer Laboratories 10³, 10⁴, 10⁵, and 10⁶),operating at a system temperature of 140° C. The solvent is1,2,4-trichlorobenzene, from which 0.3 percent by weight solutions ofthe samples are prepared for injection. The flow rate is 1.0milliliters/minute and the injection size is 200 microliters.

The molecular weight determination is deduced by using narrow molecularweight distribution polystyrene standards (from Polymer Laboratories) inconjunction with their elution volumes. The equivalent polyethylenemolecular weights are determined by using appropriate Mark-Houwinkcoefficients for polyethylene and polystyrene (as described by Williamsand Word in Journal of Polymer Science, Polymer Letters. Vol. 6, (621)1968, incorporated herein by reference) to derive the followingequation:

    M.sub.polyethylene =a*(M.sub.polystyrene).sup.b.

In this equation, a=0.4316 and b=1.0. Weight average molecular weight,M_(w), is calculated in the usual manner according to the followingformula: M_(w) =R w_(i) *M_(i), where w_(i) and M_(i) are the weightfraction and molecular weight, respectively, of the i^(th) fractioneluting from the GPC column.

Processing Index Determination

The rheological processing index (PI) is measured by a gas extrusionrheometer (GER). The GER is described by M. Shida, R. N. Shroff and L.V. Cancio in Polym. Eng. Sci., Vol. 17, no. 11, p. 770 (1977), and in"Rheometers for Molten Plastics" by John Dealy, published by VanNostrand Reinhold Co. (1982) on page 97-99, the disclosures of both ofwhich are incorporated herein by reference. The processing index ismeasured at a temperature of 190° C., at nitrogen pressure of 2500 psigusing 0.0296 inch diameter, 20:1 L/D die having an entrance angle of180°. The GER processing index is calculated in millipoise units fromthe following equation:

    PI=2.15×10.sup.6 dynes/cm.sup.2 /(1000×shear rate),

where: 2.15×10⁶ dynes/cm² is the shear stress at 2500 psi, and the shearrate is the shear rate at the wall as represented by the followingequation:

    32 Q'/ (60 sec/min)(0.745)(Diameter×2.54 cm/in).sup.3, where:

Q' is the extrusion rate (gms/min),

0.745 is the melt density of polyethylene (gm/cm³), and

Diameter is the orifice diameter of the capillary (inches). The PI isthe apparent viscosity of a material measured at apparent shear stressof 2.15×10⁶ dyne/cm².

For the substantially linear olefin polymers disclosed herein, the PI isless than or equal to 70 percent of that of a comparative linear olefinpolymer at about the same I₂ and M_(w) /M_(n). An apparent shear stressvs. apparent shear rate plot is used to identify the melt fracturephenomena. According to Ramamurthy in Journal of Rheology, 30(2),337-357, 1986, above a certain critical flow rate, the observedextrudate irregularities may be broadly classified into two main types:surface melt fracture and gross melt fracture.

Surface melt fracture occurs under apparently steady flow conditions andranges in detail from loss of specular gloss to the more severe form of"sharkskin". In this disclosure, the onset of surface melt fracture ischaracterized at the beginning of losing extrudate gloss at which thesurface roughness of extrudate can only be detected by 40×magnification.The critical shear rate at onset of surface melt fracture for thesubstantially linear olefin polymers is at least 50 percent greater thanthe critical shear rate at the onset of surface melt fracture of alinear olefin polymer having about the same I₂ and M_(w) /M_(n).

Gross melt fracture occurs at unsteady flow conditions and ranges indetail from regular (alternating rough and smooth, helical, etc.) torandom distortions. For commercial acceptability, (e.g., in blown filmproducts), surface defects should be minimal, if not absent. Thecritical shear rate at onset of surface melt fracture (OSMF) and onsetof gross melt fracture (OGMF) will be used herein based on the changesof surface roughness and configurations of the extrudates extruded by aGER.

The Constrained Geometry Catalyst

Suitable constrained geometry catalysts for use herein preferablyinclude constrained geometry catalysts as disclosed in U.S. applicationSer. Nos.: 545,403, filed Jul. 3, 1990; Ser. No. 758,654, filed Sep. 12,1991; Ser. No. 758,660, filed Sep. 12, 1991; and Ser. No. 720,041, filedJun. 24, 1991, the teachings of all of which are incorporated herein byreference. The monocyclopentadienyl transition metal olefinpolymerization catalysts taught in U.S. Pat. No. 5,026,798, theteachings of which are incorporated herein by reference, are alsosuitable for use in preparing the polymers of the present invention.

The foregoing catalysts may be further described as comprising a metalcoordination complex comprising a metal of groups 3-10 or the Lanthanideseries

of the Periodic Table of the Elements and a delocalized π-bonded moietysubstituted with a constrain-inducing moiety, said complex having aconstrained geometry about the metal atom such that the angle at themetal between the centroid of the delocalized, substituted π-bondedmoiety and the center of at least one remaining substituent is less thansuch angle in a similar complex containing a similar π-bonded moietylacking in such constrain-inducing substituent, and provided furtherthat for such complexes comprising more than one delocalized,substituted x-bonded moiety, only one thereof for each metal atom of thecomplex is a cyclic, delocalized, substituted π-bonded moiety. Thecatalyst further comprises an activating cocatalyst.

Preferred catalyst complexes correspond to the formula: ##STR1##wherein:

M is a metal of group 3-10, or the Lanthanide series of the PeriodicTable of the Elements;

Cp* is a cyclopentadienyl or substituted cyclopentadienyl group bound inan η⁵ bonding mode to M;

Z is a moiety comprising boron, or a member of group 14 of the PeriodicTable of the Elements, and optionally sulfur or oxygen, said moietyhaving up to 20 non-hydrogen atoms, and optionally Cp* and Z togetherform a fused ring system;

X independently each occurrence is an anionic ligand group or neutralLewis base ligand group having up to 30 non-hydrogen atoms;

n is 0, 1, 2, 3, or 4 and is 2 less than the valence of M; and

Y is an anionic or nonanionic ligand group bonded to Z and M comprisingnitrogen, phosphorus, oxygen or sulfur and having up to 20 non-hydrogenatoms, optionally Y and Z together form a fused ring system.

More preferably still, such complexes correspond to the formula:##STR2## wherein:

R' each occurrence is independently selected from the group consistingof hydrogen, alkyl, aryl, silyl, germyl, cyano, halo and combinationsthereof having up to 20 non-hydrogen atoms;

X each occurrence independently is selected from the group consisting ofhydride, halo, alkyl, aryl, silyl, germyl, aryloxy, alkoxy, amide,siloxy, neutral Lewis base ligands and combinations thereof having up to20 non-hydrogen atoms;

Y is --O--, --S--, --NR*--, --PR*--, or a neutral two electron donorligand selected from the group consisting of OR*, SR*, NR*₂ or PR*₂ ;

M is as previously defined; and

Z is SiR*₂, CR*₂, SiR*₂ SiR*₂, CR*₂ CR*₂, CR*═CR*, CR*₂ SiR*₂, GeR*₂,BR*, BR*₂ ; wherein

R* each occurrence is independently selected from the group consistingof hydrogen, alkyl, aryl, silyl, halogenated alkyl, halogenated arylgroups having up to 20 non-hydrogen atoms, and mixtures thereof, or twoor more R* groups from Y, Z, or both Y and Z form a fused ring system;and n is 1 or 2.

It should be noted that whereas formula I and the following formulasindicate a cyclic structure for the catalysts, when Y is a neutral twoelectron donor ligand, the bond between M and Y is more accuratelyreferred to as a coordinate-covalent bond. Also, it should be noted thatthe complex may exist as a dimer or higher oligomer.

Further preferably, at least one of R', Z, or R* is an electron donatingmoiety. Thus, highly preferably Y is a nitrogen or phosphorus containinggroup corresponding to the formula --N(R")-- or --P(R")--, wherein R" isC₁₋₁₀ alkyl or aryl, i.e., an amido or phosphido group.

Most highly preferred complex compounds are amidosilane- oramidoalkanediyl- compounds corresponding to the formula: ##STR3##wherein:

M is titanium, zirconium or hafnium, bound in an η⁵ bonding mode to thecyclopentadienyl group;

R' each occurrence is independently selected from the group consistingof hydrogen, silyl, alkyl, aryl and combinations thereof having up to 10carbon or silicon atoms;

E is silicon or carbon;

X independently each occurrence is hydride, halo, alkyl, aryl, aryloxyor alkoxy of up to 10 carbons;

m is 1 or 2; and

n is 1 or 2.

Examples of the above most highly preferred metal coordination compoundsinclude compounds wherein the R' on the amido group is methyl, ethyl,propyl, butyl, pentyl, hexyl, (including isomers), norbornyl, benzyl,phenyl, etc.; the cyclopentadienyl group is cyclopentadienyl, indenyl,tetrahydroindenyl, fluorenyl, octahydrofluorenyl, etc.; R' on theforegoing cyclopentadienyl groups each occurrence is hydrogen, methyl,ethyl, propyl, butyl, pentyl, hexyl, (including isomers), norbornyl,benzyl, phenyl, etc.; and X is chloro, bromo, iodo, methyl, ethyl,propyl, butyl, pentyl, hexyl, (including isomers), norbornyl, benzyl,phenyl, etc. Specific compounds include:(tert-butylamido)(tetramethyl-η⁵-cyclopentadienyl)-1,2-ethanediylzirconium dichloride,(tert-butylamido)(tetramethyl-η⁵ -cyclopentadienyl)1,2-ethanediyltitanium dichloride, (methylamido)(tetramethyl-η⁵-cyclopentadienyl)-1,2-ethanediylzirconium dichloride,(methylamido)(tetramethyl-η⁵ cyclopentadienyl)-1,2-ethanediyltitaniumdichloride, (ethylamido)(tetramethyl-η⁵-cyclopentadienyl)-methylenetitanium dichloro,(tertbutylamido)dibenzyl(tetramethyl-η⁵ -cyclopentadienyl)silanezirconium dibenzyl, (benzylamido)dimethyl(tetramethyl-η⁵-cyclopentadienyl)silanetitanium dichloride,(phenylphosphido)dimethyl(tetramethyl η⁵-cyclopentadienyl)silanezirconium dibenzyl,(tertbutylamido)dimethyl(tetramethyl-η⁵ -cyclopentadienyl)silanetitaniumdimethyl, and the like.

The complexes may be prepared by contacting a derivative of a metal, M,and a group I metal derivative or Grignard derivative of thecyclopentadienyl compound in a solvent and separating the saltbyproduct. Suitable solvents for use in preparing the metal complexesare aliphatic or aromatic liquids such as cyclohexane,methylcyclohexane, pentane, hexane, heptane, tetrahydrofuran, diethylether, benzene, toluene, xylene, ethylbenzene, etc., or mixturesthereof.

In a preferred embodiment, the metal compound is MX_(n+1), i.e., M is ina lower oxidation state than in the corresponding compound, MX_(n+2) andthe oxidation state of M in the desired final complex. A noninterferingoxidizing agent may thereafter be employed to raise the oxidation stateof the metal. The oxidation is accomplished merely by contacting thereactants utilizing solvents and reaction conditions used in thepreparation of the complex itself. By the term "noninterfering oxidizingagent" is meant a compound having an oxidation potential sufficient toraise the metal oxidation state without interfering with the desiredcomplex formation or subsequent polymerization processes. A particularlysuitable noninterfering oxidizing agent is AgCl or an organic halidesuch as methylene chloride. The foregoing techniques are disclosed inU.S. Ser. Nos.: 545,403, filed Jul. 3, 1990 and Ser. No. 702,475, filedMay 20, 1991, the teachings of both of which are incorporated herein byreference.

Additionally the complexes may be prepared according to the teachings ofthe copending application serial number 778,433 entitled: "Preparationof Metal Coordination Complex (I)", filed in the names of Peter Nickiasand David Wilson, on Oct. 15, 1991 and the copending application Ser.No. 778,432 entitled: "Preparation of Metal Coordination Complex (II)",filed in the names of Peter Nickias and David Devore, on Oct. 15, 1991,the teachings of which are incorporated herein by reference thereto.

Suitable cocatalysts for use herein include polymeric or oligomericaluminoxanes, especially methyl aluminoxane, as well as inert,compatible, noncoordinating, ion forming compounds. So-called modifiedmethyl aluminoxane (MMAO) is also suitable for use as a cocatlyst. Onetechnique for preparing such modified aluminoxane is disclosed in U.S.Pat. No. 5,041,584, the teachings of which are incorporated herein byreference. Aluminoxanes can also be made as disclosed in U.S. Pat. Nos.5,542,199; 4,544,762; 5,015,749; and 5,041,585, the entire specificationof each of which is incorporated herein by reference. Preferredcocatalysts are inert, noncoordinating, boron compounds.

Ionic active catalyst species which can be used to polymerize thepolymers described herein correspond to the formula: ##STR4## wherein:

M is a metal of group 3-10, or the Lanthanide series of the PeriodicTable of the Elements;

Cp* is a cyclopentadienyl or substituted cyclopentadienyl group bound inan η⁵ bonding mode to M;

Z is a moiety comprising boron, or a member of group 14 of the PeriodicTable of the Elements, and 20 optionally sulfur or oxygen, said moietyhaving up to 20 non-hydrogen atoms, and optionally Cp* and Z togetherform a fused ring system;

X independently each occurrence is an anionic ligand group or neutralLewis base ligand group having up to 30 non-hydrogen atoms;

n is 0, 1, 2, 3, or 4 and is 2 less than the valence of M; and

A- is a noncoordinating, compatible anion.

One method of making the ionic catalyst species which can be utilized tomake the polymers of the present invention involve combining:

a) at least one first component which is a mono(cyclopentadienyl)derivative of a metal of Group 3-10 or the Lanthanide Series of thePeriodic Table of the Elements containing at least one substituent whichwill combine with the cation of a second component (describedhereinafter) which first component is capable of forming a cationformally having a coordination number that is one less than its valence,and

b) at least one second component which is a salt of a Bronsted acid anda noncoordinating, compatible anion.

More particularly, the non-coordinating, compatible anion of theBronsted acid salt may comprise a single coordination complex comprisinga charge-bearing metal or metalloid core, which anion is both bulky andnon-nucleophilic. The recitation "metalloid", as used herein, includesnon metals such as boron, phosphorus and the like which exhibitsemi-metallic characteristics.

Illustrative, but not limiting examples of monocyclopentadienyl metalcomponents (first components) which may be used in the preparation ofcationic complexes are derivatives of titanium, zirconium, vanadium,hafnium, chromium, lanthanum, etc. Preferred components are titanium orzirconium compounds. Examples of suitable monocyclopentadienyl metalcompounds are hydrocarbyl-substituted monocyclopentadienyl metalcompounds such as (tert-butylamido)(tetramethyl-η⁵-cyclopentadienyl)-1,2-ethanediylzirconium dimethyl,(tertbutylamido)(tetramethyl-η⁵-cyclopentadienyl)-1,2-ethanediyltitanium dimethyl,(methylamido)(tetramethyl-η⁵ -cyclopentadienyl)-1,2-ethanediylzirconiumdibenzyl, (methylamido)(tetramethyl-η⁵-cyclopentadienyl)-1,2-ethanediyltitanium dimethyl,(ethylamido)(tetramethyl η⁵ -cyclopentadienyl)methylenetitaniumdimethyl, (tertbutylamido)dibenzyl(tetramethyl-η⁵ -cyclopentadienyl)silanezirconium dibenzyl, (benzylamido)dimethyl(tetramethyl-η⁵-cyclopentadienyl)silanetitanium diphenyl,(phenylphosphido)dimethyl(tetramethyl-η⁵-cyclopentadienyl)silanezirconium dibenzyl, and the like.

Such components are readily prepared by combining the correspondingmetal chloride with a dilithium salt of the substituted cyclopentadienylgroup such as a cyclopentadienyl-alkanediyl, cyclopentadienyl--silaneamide, or cyclopentadienyl--phosphide compound. The reaction isconducted in an inert liquid such as tetrahydrofuran, C₅₋₁₀ alkanes,toluene, etc. utilizing conventional synthetic procedures. Additionally,the first components may be prepared by reaction of a group IIderivative of the cyclopentadienyl compound in a solvent and separatingthe salt by-product. Magnesium derivatives of the cyclopentadienylcompounds are preferred. The reaction may be conducted in an inertsolvent such as cyclohexane, pentane, tetrahydrofuran, diethyl ether,benzene, toluene, or mixtures of the like. The resulting metalcyclopentadienyl halide complexes may be alkylated using a variety oftechniques. Generally, the metal cyclopentadienyl alkyl or arylcomplexes may be prepared by alkylation of the metal cyclopentadienylhalide complexes with alkyl or aryl derivatives of group I or group IImetals. Preferred alkylating agents are alkyl lithium and Grignardderivatives using conventional synthetic techniques. The reaction may beconducted in an inert solvent such as cyclohexane, pentane,tetrahydrofuran, diethyl ether, benzene, toluene, or mixtures of thelike. A preferred solvent is a mixture of toluene and tetrahydrofuran.

Compounds useful as a second component in the preparation of the ioniccatalysts useful in this invention will comprise a cation, which is aBronsted acid capable of donating a proton, and a compatiblenoncoordinating anion. Preferred anions are those containing a singlecoordination complex comprising a charge-bearing metal or metalloid corewhich anion is relatively large (bulky), capable of stabilizing theactive catalyst species (the Group 3-10 or Lanthanide Series cation)which is formed when the two components are combined and sufficientlylabile to be displaced by olefinic, diolefinic and acetylenicallyunsaturated substrates or other neutral Lewis bases such as ethers,nitriles and the like. Suitable metals, then, include, but are notlimited to, aluminum, gold, platinum and the like. Suitable metalloidsinclude, but are not limited to, boron, phosphorus, silicon and thelike. Compounds containing anions which comprise coordination complexescontaining a single metal or metalloid atom are, of course, well knownand many, particularly such compounds containing a single boron atom inthe anion portion, are available commercially. In light of this, saltscontaining anions comprising a coordination complex containing a singleboron atom are preferred.

Highly preferably, the second component useful in the preparation of thecatalysts of this invention may be represented by the following generalformula:

    (L-H).sup.+  [A].sup.-

wherein:

L is a neutral Lewis base;

(L-H)⁺ is a Bronsted acid; and

[A]- is a compatible, noncoordinating anion.

More preferably [A]⁻ corresponds to the formula:

    [M'Qq].sup.-

wherein:

M' is a metal or metalloid selected from Groups 5-15 of the PeriodicTable of the Elements; and

Q independently each occurrence is selected from the Group consisting ofhydride, dialkylamido, halide, alkoxide, aryloxide, hydrocarbyl, andsubstituted-hydrocarbyl radicals of up to 20 carbons with the provisothat in not more than one occurrence is Q halide and

q is one more than the valence of M'.

Second components comprising boron which are particularly useful in thepreparation of catalysts of this invention may be represented by thefollowing general formula:

    [L-H].sup.+  [BQ.sub.4 ].sup.-

wherein:

L is a neutral Lewis base;

[L-H]⁺ is a Bronsted acid;

B is boron in a valence state of 3; and

Q is as previously defined.

Illustrative, but not limiting, examples of boron compounds which may beused as a second component in the preparation of the improved catalystsof this invention are trialkyl-substituted ammonium salts such astriethylammonium tetraphenylborate, tripropylammonium tetraphenylborate,tris(n-butyl)ammonium tetraphenylborate, trimethylammoniumtetrakis(p-tolyl)borate, tributylammoniumtetrakis(pentafluorophenyl)borate, tripropylammoniumtetrakis(2,4-dimethylphenyl)borate, tributylammoniumtetrakis(3,5-dimethylphenyl)borate, triethylammoniumtetrakis(3,5-di-trifluoromethylphenyl)borate and the like. Also suitableare N,N-dialkyl anilinium salts such asN,N-dimethyl-aniliniumtetraphenylborate, N,N-diethylaniliniumtetraphenylborate, N,N-2,4,6-pentamethylanilinium tetraphenylborate andthe like; dialkylammonium salts such as di-(i-propyl)ammoniumtetrakis(pentafluorophenyl)borate, dicyclohexylammoniumtetraphenylborate and the like; and triaryl phosphonium salts such astriphenylphosphonium tetraphenylborate, tri(methylphenyl)phosphoniumtetrakispentafluorophenylborate, tri(dimethylphenyl)phosphoniumtetraphenylborate and the like.

Preferred ionic catalysts are those having a limiting charge separatedstructure corresponding to the formula: ##STR5## wherein:

M is a metal of group 3-10, or the Lanthanide series of the PeriodicTable of the Elements;

Cp* is a cyclopentadienyl or substituted cyclopentadienyl group bound inan η⁵ bonding mode to M;

Z is a moiety comprising boron, or a member of group 14 of the PeriodicTable of the Elements, and optionally sulfur or oxygen, said moietyhaving up to 20 non-hydrogen atoms, and optionally Cp* and Z togetherform a fused ring system;

X independently each occurrence is an anionic ligand group or neutralLewis base ligand group having up to 30 non-hydrogen atoms;

n is 0, 1, 2, 3, or 4 and is 2 less than the valence of M; and

XA*- is ⁻ XB(C₆ F₅)₃.

This class of cationic complexes may be conveniently prepared bycontacting a metal compound corresponding to the formula: ##STR6##wherein:

Cp*. M, and n are as previously defined, withtris(pentafluorophenyl)borane cocatalyst under conditions to causeabstraction of X and formation of the anion ⁻ XB(C₆ F₅)₃.

Preferably X in the foregoing ionic catalyst is C₁ C₁₀ hydrocarbyl, mostpreferably methyl.

The preceding formula is referred to as the limiting, charge separatedstructure. However, it is to be understood that, particularly in solidform, the catalyst may not be fully charge separated. That is, the Xgroup may retain a partial covalent bond to the metal atom, M. Thus, thecatalysts may be alternately depicted as possessing the formula:##STR7##

The catalysts are preferably prepared by contacting the derivative of aGroup 4 or Lanthanide metal with the tris(pentafluorophenyl)borane in aninert diluent such as an organic liquid. Tris(pentafluorphenyl)borane isa commonly available Lewis acid that may be readily prepared accordingto known techniques. The compound is disclosed in Marks, et al. J. Am.Chem. Soc. 1991, 113, 3623-3625 for use in alkyl abstraction ofzirconocenes.

All reference to the Periodic Table of the Elements herein shall referto the Periodic Table of the Elements, published and copyrighted by CRCPress, Inc., 1989. Also, any reference to a Group or Groups shall be tothe Group or Groups as reflected in this Periodic Table of the Elementsusing the IUPAC system for numbering groups.

It is believed that in the constrained geometry catalysts used hereinthe metal atom is forced to greater exposure of the active metal sitebecause one or more substituents on the single cyclopentadienyl orsubstituted metal is both bonded to an adjacent covalent moiety and heldin association with the cyclopentadienyl group through an η⁵ or otherπ-bonding interaction. It is understood that each respective bondbetween the metal atom and the constituent atoms of the cyclopentadienylor substituted cyclopentadienyl group need not be equivalent. That is,the metal may be symmetrically or unsymmetrically π-bound to thecyclopentadienyl or substituted cyclopentadienyl group.

The geometry of the active metal site is further defined as follows. Thecentroid of the cyclopentadienyl or substituted cyclopentadienyl groupmay be defined as the average of the respective X, Y, and Z coordinatesof the atomic centers forming the cyclopentadienyl or substitutedcyclopentadienyl group. The angle, Θ, formed at the metal center betweenthe centroid of the cyclopentadienyl or substituted cyclopentadienylgroup and each other ligand of the metal complex may be easilycalculated by standard techniques of single crystal X-ray diffraction.Each of these angles may increase or decrease depending on the molecularstructure of the constrained geometry metal complex. Those complexeswherein one or more of the angles, Θ, is less than in a similar,comparative complex differing only in the fact that the constraininducing substituent is replaced by hydrogen, have constrained geometryfor purposes of the present invention. Preferably one or more of theabove angles, Θ, decrease by at least 5 percent, more preferably 7.5percent, compared to the comparative complex. Highly preferably, theaverage value of all bond angles, Θis also less than in the comparativecomplex.

Preferably, monocyclopentadienyl metal coordination complexes of group 4or lanthanide metals according to the present invention have constrainedgeometry such that the smallest angle, Θ between the centroid of the Cp*group and the Y substituent, is less than 115°, more preferably lessthan 110°, most preferably less than 105°, and especially less than100°.

Other compounds which are useful in the catalyst compositions of thisinvention, especially compounds containing other Group 4 or Lanthanidemetals, will, of course, be apparent to those skilled in the art.

Polymerization

The polymerization conditions for manufacturing the polymers of thepresent invention are generally those useful in the solutionpolymerization process, although the application of the presentinvention is not limited thereto. Slurry and gas phase polymerizationprocesses are also believed to be useful, provided the proper catalystsand polymerization conditions are employed.

Multiple reactor polymerization processes are also useful in the presentinvention, such as those disclosed in U.S. Pat. No. 3,914,342,incorporated herein by reference. The multiple reactors can be operatedin series or in parallel, with at least one constrained geometrycatalyst employed in at least one of the reactors.

In general, the continuous polymerization according to the presentinvention may be accomplished at conditions well known in the prior artfor Ziegler-Natta or Kaminsky-Sinn type polymerization reactions, thatis, temperatures from 0° to 250° C. and pressures from atmospheric to1000 atmospheres (100 MPa). Suspension, solution, slurry, gas phase orother process conditions may be employed if desired. A support may beemployed but preferably the catalysts are used in a homogeneous (i.e.,soluble) manner. It will, of course, be appreciated that the activecatalyst system, especially nonionic catalysts, form in situ if thecatalyst and the cocatalyst components thereof are added directly to thepolymerization process and a suitable solvent or diluent, includingcondensed monomer, is used in said polymerization process. It is,however, preferred to form the active catalyst in a separate step in asuitable solvent prior to adding the same to the polymerization mixture.

The polymerization conditions for manufacturing the polymers of thepresent invention are generally those useful in the solutionpolymerization process, although the application of the presentinvention is not limited thereto. Gas phase polymerization processes arealso believed to be useful, provided the proper catalysts andpolymerization conditions are employed.

Fabricated articles made from the novel olefin polymers may be preparedusing all of the conventional polyolefin processing techniques. Usefularticles include films (e.g., cast, blown and extrusion coated), fibers(e.g., staple fibers (including use of a novel olefin polymer disclosedherein as at least one component comprising at least a portion of thefiber's surface), spunbound fibers or melt blown fibers (using, e.g.,systems as disclosed in U.S. Pat. No. 4,340,563, U.S. Pat. No.4,663,220, U.S. Pat. No. 4,668,566, or U.S. Pat. No. 4,322,027, all ofwhich are incorporated herein by reference), and gel spun fibers (e.g.,the system disclosed in U.S. Pat. No. 4,413,110, incorporated herein byreference)), both woven and nonwoven fabrics (e.g., spunlaced fabricsdisclosed in U.S. Pat. No. 3,485,706, incorporated herein by reference)or structures made from such fibers (including, e.g., blends of thesefibers with other fibers, e.g., PET or cotton) and molded articles(e.g., made using an injection molding process, a blow molding processor a rotomolding process). The new polymers described herein are alsouseful for wire and cable coating operations, impact modification,especially at low temperatures, of thermoplastic olefins (e.g.,polypropylene), as well as in sheet extrusion for vacuum formingoperations.

Useful compositions are also suitably prepared comprising thesubstantially linear polymers of the present invention and at least oneother natural or synthetic polymer. Preferred other polymers includethermoplastics such as styrene-butadiene block copolymers, polystyrene(including high impact polystyrene), ethylene vinyl alcohol copolymers,ethylene acrylic acid copolymers, other olefin copolymers (especiallypolyethylene copolymers) and homopolymers (e.g., those made usingconventional heterogeneous catalysts). Examples include polymers made bythe process of U.S. Pat. No. 4,076,698, incorporated herein byreference, other linear or substantially linear polymers of the presentinvention, and mixtures thereof. Other substantially linear polymers ofthe present invention and conventional HDPE and/or LLDPE are preferredfor use in the thermoplastic compositions.

Compositions comprising the olefin polymers can also be formed intofabricated articles such as those previously mentioned usingconventional polyolefin processing techniques which are well known tothose skilled in the art of polyolefin processing.

All procedures were performed under an inert atmosphere or nitrogen orargon. Solvent choices were often optional, for example, in most caseseither pentane or 30-60 petroleum ether can be interchanged. Amines,silanes, lithium reagents, and Grignard reagents were purchased fromAldrich Chemical Company. Published methods for preparingtetramethylcyclopentadiene (C₅ Me₄ H₂) and lithiumtetramethylcyclopentadienide (Li(C₅ Me₄ H)) include C. M. Fendrick etal. Organometallics, 3, 819 (1984). Lithiated substitutedcyclopentadienyl compounds may be typically prepared from thecorresponding cyclopentadiene and a lithium reagent such as n-butyllithium. Titanium trichloride (TiC₁₃) was purchased from AldrichChemical Company. The tetrahydrofuran adduct of titanium trichloride,TiC₁₃ (THF)₃, was prepared by refluxing TiC₁₃ in THF overnight, cooling,and isolating the blue solid product, according to the procedure of L.E. Manzer, Inorg. Syn., 21, 135 (1982).

EXAMPLES

The polymer products of Examples 1 and 3 are produced in a continuoussolution polymerization process using a continuously stirred reactor, asdescribed in copending application serial number 07/776,130, filed Oct.15, 1991. The metal complex [C₅ Me₄ (SiMe₂ N^(t) Bu)]TiMe₂ is preparedas described in copending application Ser. No. 07/776,130 and thecocatalysts used are tris(pentafluorophenyl) borane (B:Ti ratio of 2:1)and MMAO (Al:Ti ratio of 4:1). For Example 1 the ethylene concentrationin the reactor is about 1.10% and for Example 3 the ethyleneconcentration in the reactor is about 1.02% (percentages based on theweight of the reactor contents). For each Example, the reactor is runwithout hydrogen.

Additives (e.g., antioxidants, pigments, etc.) can be incorporated intothe interpolymer products either during the pelletization step or aftermanufacture, with a subsequent re-extrusion. Examples 1 and 3 are eachstabilized with 1250 ppm Calcium Stearate, 200 ppm Irganox 1010, and1600 ppm Irgafos 168. Irgafos™ 168 is a phosphite stabilizer andIrganox™ 1010 is a hindered polyphenol stabilizer (e.g., tetrakis[methylene 3-(3,5-ditert.butyl-4-hydroxyphenylpropionate)]methane. Bothare trademarks of and made by Ciba-Geigy Corporation.

Example 1 and Comparative Example 2

Example 1 is an ethylene/1 octene elastic substantially linear olefinpolymer produced as described herein.

Comparative Example 2 is an ethylene/1-butene copolymer containingbutylated hydroxy toluene (BHT) and Irganox™ 1076 made by Exxon Chemicaland trademarked Exact™. Table 1 summarizes physical properties andrheological performance of these two polymers:

                  TABLE 1                                                         ______________________________________                                                                  Comparative                                         Property        Example 1 Example 2                                           ______________________________________                                        I.sub.2         3.3       3.58                                                (g/10 minutes)                                                                Density         0.870     0.878                                               (g/cm.sup.3)                                                                  I.sub.10 /I.sub.2                                                                             7.61      5.8                                                 M.sub.w /M.sub.n                                                                              1.97      1.95                                                PI              3.2       8.4                                                 (kPoise)                                                                      Elastic Modulus @                                                                             87.7      8.3                                                 0.1 rad/sec                                                                   (dynes/cm.sup.2)                                                              OSMF*, critical 660       250                                                 shear rate (sec.sup.-1)                                                       ______________________________________                                         *Onset of surface melt fracture                                          

Even though Example 1 and Comparative Example 2 have very similarmolecular weight distributions (M_(w) /M_(n)), I₂ and density, Example 1has a much lower processing index (PI) (38% of the PI of ComparativeExample 2), a much higher onset of surface melt fracture (264% increasein OSMF) and an elastic modulus an order of magnitude higher thanComparative Example 2, demonstrating that Example 1 has much betterprocessability and higher melt elasticity than Comparative Example 2.

Elastic modulus is indicative of a polymer's melt stability, e.g., morestable bubbles when making blown film and less neck-in. Resultantphysical properties of the finished film are also higher.

Onset of surface melt fracture is easily identified by visuallyobserving the surface extrudate and noting when the extrudate startslosing gloss and small surface roughness is detected by using40×magnification.

Dynamic shear viscosity of the polymers is also used to show differencesbetween the polymers and measures viscosity change versus shear rate. ARheometrics Mechanical Spectrometer (Model RMS 800) is used to measureviscosity as a function of shear rate. The RMS 800 is used at 190° C. at15% strain and a frequency sweep (i.e., from 0.1-100 rad/sec) under anitrogen purge. The parallel plates are positioned such that they have agap of about 1.5-2 mm. Data for Example 1 and Comparative Example 2 arelisted in Table 2 and graphically displayed in FIG. 1.

                  TABLE 2                                                         ______________________________________                                                    Dynamic     Dynamic Viscosity                                                 Viscosity   (poise)                                               Shear Rate  (poise)     for Comparative                                       (rad/sec)   for Example 1                                                                             Example 2                                             ______________________________________                                        0.1         28290       18990                                                 0.1585      28070       18870                                                 0.2512      27630       18950                                                 0.3981      27140       18870                                                 0.631       26450       18840                                                 1           25560       18800                                                 1.585       24440       18690                                                 2.512       23140       18540                                                 3.981       21700       18310                                                 6.31        20170       17960                                                 10          18530       17440                                                 15.85       16790       16660                                                 25.12       14960       15620                                                 39.81       13070       14310                                                 63.1        11180       12750                                                 100          9280       10960                                                 ______________________________________                                    

Surprisingly, Example 1 shows a shear thinning behaviour, even thoughExample 1 has a narrow molecular weight distribution. In contrast,Comparative Example 2 shows the expected behaviour of a narrow molecularweight distribution polymer, with a flatter viscosity/shear rate curve.

Thus, elastic substantially linear olefin polymers made in accordancewith the present invention (e.g. Example 1) have lower melt viscositythan a typical narrow molecular weight distribution linear copolymermade by single site catalyst technology at the melt processing shearrate region of commercial interest. In addition, the novel elasticsubstantially linear olefin polymers have a higher low shear/zero shearviscosity than the Comparative linear polymer, thus demonstrating thatthe copolymers of the invention have higher "green strength" which isuseful for forming and maintaining blended compositions such as thoseused in the wire and cable coating industry, where the compoundedmaterials must maintain their integrity at low or zero shear withoutsegregating the components.

Example 3 and Comparative Example 4

Example 3 is an ethylene/1-octene elastic substantially linear olefinpolymer produced in a continuous solution polymerization process asdescribed herein.

Comparative Example 4 is an ethylene/1-propene copolymer made by MitsuiPetroChemical Corporation and trademarked Tafmer™ P-0480. Table 3summarizes physical properties and rheological performance of these twopolymers:

                  TABLE 3                                                         ______________________________________                                                                  Comparative                                         Property        Example 3 Example 4                                           ______________________________________                                        I.sub.2         1.01      1.1                                                 (g/10 minutes)                                                                Density         0.870     0.870                                               (g/cm.sup.3)                                                                  I.sub.10 /I.sub.2                                                                             7.62      6.06                                                M.sub.w /M.sub.n                                                                              1.98      1.90                                                PI              7.9       27.4                                                (kPoise)                                                                      Elastic Modulus @                                                                             964       567.7                                               0.1 rad/sec                                                                   (dynes/cm.sup.2)                                                              OSMF*, critical 781       105                                                 shear rate (sec.sup.-1)                                                       ______________________________________                                         *Onset of surface melt fracture                                          

Even though Example 3 and Comparative Example 4 have similarly narrowmolecular weight distributions (M_(w) /M_(n)), I₂, and density, Example3 has a PI which is 28% of that of Comparative Example 4, a 743%increase in onset of surface melt fracture and a higher elastic modulusthan Comparative Example 4, demonstrating that Example 3 has much betterprocessability than Comparative Example 4. Onset of surface meltfracture is easily identified by visually observing the surfaceextrudate and noting when the extrudate starts losing gloss and smallsurface roughness is detected by using 40×magnification.

We claim:
 1. A substantially linear olefin polymer characterized ashaving:a) a melt flow ratio, I₁₀ /I₂,≧5.63, b) a molecular weightdistribution, M_(w) /M_(n), defined by the equation:

    M.sub.w /M.sub.n ≦(I.sub.10 /I.sub.2)-4.63, and

c) a critical shear rate at onset of surface melt fracture of at least50 percent greater than the critical shear rate at the onset of surfacemelt fracture of a linear olefin polymer having about the same I₂ andM_(w) /M_(n), and wherein the olefin polymer is further characterized asa copolymer of ethylene with a C₃ -C₂₀ alpha-olefin.
 2. Thesubstantially linear olefin polymer of claim 1 wherein the M_(w) /M_(n)is less than about 3.5.
 3. The substantially linear olefin polymer ofclaim 1 wherein the M_(w) /M_(n) is from about 1.5 to about 2.5.
 4. Thesubstantially linear olefin polymer of claim 3 wherein the I₁₀ /I₂ is atleast about
 8. 5. The substantially linear olefin polymer of claim 3wherein the I₁₀ /I₂ is at least about
 9. 6. The substantially linearolefin polymer of claim 1 wherein the polymer is a substantially linearethylene polymer having from about 0.01 to about 3 long chainbranches/1000 carbons along the polymer backbone.
 7. The substantiallylinear olefin polymer of claim 4 having at least about 0.05 long chainbranches/1000 carbons along the polymer backbone.
 8. The substantiallylinear olefin polymer of claim 4 having at least about 0.3 long chainbranches/1000 carbons along the polymer backbone.
 9. The substantiallylinear olefin polymer of claim 1, wherein the polymer is a copolymer ofethylene and 1-octene.
 10. The substantially linear olefin polymer ofclaim 1, wherein the polymer is a copolymer of ethylene and 1-hexene.11. The substantially linear olefin polymer of claim 1, wherein thepolymer is a copolymer of ethylene and 1-butene.
 12. The substantiallylinear olefin polymer of claim 1, wherein the polymer is a copolymer ofethylene and 4-methyl-1-pentene.
 13. The substantially linear olefinpolymer of claim 1, wherein the polymer is a copolymer of ethylene and1-octene.
 14. The substantially linear olefin polymer of claim 1,wherein the polymer is a copolymer of ethylene and 1-hexene.
 15. Thesubstantially linear olefin polymer of claim 1, wherein the polymer is acopolymer of ethylene and 1-butene.
 16. The substantially linear olefinpolymer of claim 1, wherein the polymer is a copolymer of ethylene and4-methyl-1-pentene.
 17. A composition comprising a substantially linearolefin polymer, wherein the polymer is characterized as having:a) a meltflow ratio, I₁₀ /I₂,≧5.63, b) a molecular weight distribution, M_(w)/M_(n), defined by the equation:

    M.sub.w /M.sub.n ≦(I.sub.10 /I.sub.2)-4.63, and

c) a critical shear rate at onset of surface melt fracture of at least50 percent greater than the critical shear rate at the onset of surfacemelt fracture of a linear olefin polymer having about the same I₂ andM_(w) /M_(n), and wherein the olefin polymer is further characterized asa copolymer of ethylene with a C₃ -C₂₀ alpha-olefin and (b) at least oneother natural or synthetic polymer.
 18. The composition of claim 17wherein the substantially linear olefin polymer has a I₁₀ /I₂ up toabout
 20. 19. The composition of claim 17 wherein the substantiallylinear olefin polymer has a M_(w) /M_(n) less than about 3.5.
 20. Thecomposition of claim 17 wherein the substantially linear olefin polymerhas a M_(w) /M_(n) from about 1.5 to about 2.5.
 21. The composition ofclaim 17 wherein the synthetic polymer is a conventional olefin polymer.22. The composition of claim 17, wherein the substantially linear olefinpolymer is a copolymer of ethylene and 1-octene.
 23. The composition ofclaim 17, wherein the substantially linear olefin polymer is a copolymerof ethylene and 1-hexene.
 24. The composition of claim 17, wherein thesubstantially linear olefin polymer is a copolymer of ethylene and1-butene.
 25. The composition of claim 17, wherein the substantiallylinear olefin polymer is a copolymer of ethylene and 4-methyl-1-pentene.26. A substantially linear olefin polymer characterized as a copolymerof ethylene with a C₃ -C₂₀ alpha-olefin and having:a) a melt flow ratio,I₁₀ /I₂,≧5.63, b) a molecular weight distribution, M_(w) /M_(n), definedby the equation:

    M.sub.w /M.sub.n ≦(I.sub.10 /I.sub.2)-4.63, and

c) a processing index (PI) less than or equal to about 70% of the PI ofa comparative linear olefin polymer at about the same I₂ and M_(w)/M_(n).
 27. The substantially linear olefin polymer of claim 1, whereinthe polymer is in pelletized form.
 28. The pelletized substantiallylinear olefin polymer of claim 27, wherein the density of the polymer isfrom about 0.85 g/cm³ to about 0.9 g/cm³.
 29. The pelletizedsubstantially linear olefin polymer of claim 27, wherein the density ofthe polymer is from about 0.85 g/cm³ to about 0.88 g/cm³.
 30. Thesubstantially linear olefin polymer of claim 1, wherein the polymer isin pelletized form.
 31. The pelletized substantially linear olefinpolymer of claim 30, wherein the density of the polymer is from about0.85 g/cm³ to about 0.9 g/cm³.
 32. The pelletized substantially linearolefin polymer of claim 30, wherein the density of the polymer is fromabout 0.85 g/cm³ to about 0.88 g/cm³.
 33. The substantially linearolefin polymer of claim 26, wherein the polymer is in pelletized form.34. The pelletized substantially linear olefin polymer of claim 33,wherein the density of the polymer is from about 0.85 g/cm³ to about 0.9g/cm³.
 35. The pelletized substantially linear olefin polymer of claim33, wherein the density of the polymer is from about 0.85 g/cm³ to about0.88 g/cm³.
 36. A film layer comprising a substantially linear olefinpolymer, wherein the substantially linear olefin polymer ischaracterized as having:a) a melt flow ratio, I₁₀ /I₂,≧5.63, b) amolecular weight distribution, M_(w) /M_(n), defined by the equation:

    M.sub.w /M.sub.n ≦(I.sub.10 /I.sub.2)-4.63, and

c) a critical shear rate at onset of surface melt fracture at least 50percent greater than the critical shear rate at the onset of surfacemelt fracture of a linear olefin polymer having about the same I₂ andM_(w) /M_(n), and wherein the olefin polymer is further characterized asa copolymer of ethylene with a C₃ -C₂₀ alpha-olefin.
 37. A film layercomposition comprising a substantially linear olefin polymer, whereinthe substantially linear olefin polymer is characterized as having:a) amelt flow ratio, I₁₀ /I₂,≧5.63, b) a molecular weight distribution,M_(w) /M_(n), of from 1.5 to 2.5, and c) a critical shear rate at onsetof surface melt fracture of at least 50 percent greater than thecritical shear rate at the onset of surface melt fracture of a linearolefin polymer at about the same I₂ and M_(w) /M_(n), and wherein theolefin polymer is further characterized as a copolymer of ethylene witha C₃ -C₂₀ alpha-olefin.